Use blogging software or the blogging feature of your school's course management system and require students to make one post each week reflecting on the class, editing or errors they have discovered. If it is a large class, split it and have each half do alternate weeks. Require that each post have at least one relevant link.

But then here's the twist. On certain weeks, which you do not disclose beforehand (so the students don't salt a post with errors), tell each student to go in and edit his or her post, both correcting errors and for brevity. I usually require before and after printed versions for ease of grading and give extra credit based on how many errors they catch and the relevance of links. (I give one point back for each error and a total of three possible for good links). Set a maximum number of points back, and if you have someone doing a perfect post that needs no editing, then give him or her the maximum (you also can adjust for near-perfect posts).

The writing and editing noticeably sharpen throughout the semester. As an alternative, I have also done this with my course management system's wiki software – requiring each student to post a short profile at the beginning of the semester and then, after the first couple weeks of review, making students go back and edit their profiles.